This invention relates to an end closure construction for a tube-type carton, such as a paperboard carton for containing milk, juices, or other liquids.
Typically, a roll of paperboard is often extrusion coated with barrier laminations of polymers and foils for the purpose of rendering the eventual paperboard container liquid tight and provide the required product protection, with the blank thereafter being folded and heat sealed to define an erected or completed container. Such cartons are fashioned from a single blank of paperboard, suitably scored so as to provide desired fold or hinged lines.
A variety of end closure constructions for such tube-type containers is known. For example, one well known construction is the so-called gable top construction commonly employed for milk cartons. The bottom of such a carton is closed in such a manner that it is flat, while the upper portion is provided with a top in the form of a gable (house) roof, with the top being opened by the consumer to define a pour spout, the spout usually being reclosable.
Another type of end closure for the top of such a carton is a flat-topped end closure which is the same container without the gable, the end closure instead being fin sealed with the fin being folded over. Such closures for the top of a liquid carrying container exhibited the advantage of being easier to store because the carton has a flat top. Often, such flat-topped containers suffer the drawback of overlapping of several paperboard layers at the center of the closure. Such multiple thicknesses of paperboard are sometimes difficult to seal properly by use of heat and pressure and further exhibit the drawback of exposed paperboard edges and stress cracking of the barrier materials. These edges and cracks allow for migration of bacteria, oxygen, and wetting of the product into any exposed fibers of the paperboard which may be present. Thus, the product freshness and shelf life are shortened.